If i am clear on your question.. you need the correct faction privs.. then click the [View/Set Arrest Options] tab and the last set of options are for your NPCs reaction to an arrest.. now you have to take into consideration the concept of A/E. This being said there are very few NPCs that would be strong enough to stop an arrest attempt. Now it does happen at random that one or two might run and hide but the majority of the time they will be arrested and killed, and the one or two that might escape normally can not do it twice. I hope this helps a bit.